Cleaning composition



Patented Aug. 1, 1939 UNETED fiTATES CLEANING COMPOSITION George R.Ensminger, New Brunswick, N. J., assignor to E. 1. du Pont de Nemours &Company, Wilmington, Del., a corporation oi Delaware No Drawing.Application November 12, 1936, Serial No. 110,473

'1 Claims.

This invention relates to an improved cleaning composition and moreparticularly to a cleaning composition which is particularly adapted forpreparing previously coated surfaces for refinishing. Heretofore,particularly in refinishing automobiles, the old surface was subjectedto the slow and tedious process of sanding with gasoline and water. Thistreatment is effective in removing grease, wax, tar, and the like fromthe surface, but has the disadvantage that the old paint or lacquerwhich remains is usually scratched. When the new coating is applied, thesolvents attack the old finish more along the scratches than on theunscratched area. This produces uneven swelling of the old finish andcauses so-called welts to appear. In order to eliminate this, a shellacor shellac substitute sealer coat is often applied to the sandpaperedsurface prior to the application of the enamel.

An object of the present invention is the provision of a cleaningcomposition which quickly and efliciently removes dirt, grime, tar, and1101- lshing wax from the old surface without the use of abrasives.

Another object of this invention is the provision of a cleaner whichpromotes adhesion of the new finish to the old.

A still further object of the invention is the preparation of a surfacefor refinishing which is charadterized by exceptional smoothness andabsence of irregularities such as scratches, welts and the like. Otherobjects of the invention will become apparent as the descriptionproceeds.

' These objects are accomplished by the use of a cleaning compositionwhich contains a plurality of ingredients of at least two or threedifferent classes.

The main class of compounds in the composition with respect to volume isrepresented by solvents for grease. wax and tar. These may be xylol,toluol, high boiling naphtha, mineral spirits, chlorinated hydrocarbons,hydrogenated naphtha, and usually a solvent such as turpentine which hasa relatively low rate of volatility. The second class is present in muchsmaller amounts and is usually a lacquer solvent having a relativelyhigh boiling point although the compositions which are satisfactorycannot be satisfactorily defined by the range of their boiling points.It has been found that the class of compounds which are satisfactory maybe defined by their penetration power into a dried nitrocellulose filmand also their evaporation rates as will be more fully describedhereinafter.

I prefer to designate compounds of this class as activators.

The third class in the composition is a blanketing agent which servesthe purpose of holding the other constituents of the cleaner in contactwith the surface as long as is needed. The ingredients representing thisclass are present in relatively small amounts; that is, of the order ofabout 1% and are usually solvent plasticizers for the cellulosederivative.

The following examples are given to illustrate how the invention may becarried out. The following compositions are prepared by mixing theingredients in any convenient manner and in any order:

Example 1 Per cent by weight Xylol 30.0

High boiling naphtha (B. R., 160 to 180 C.) 10.0 Mineral spirits (B. R.,150 to 225 C.) 21.0 Hydrogenated naphtha (B. R... to 190 C.) 17.0Turpentine 15.0 Butyl lactate 6.0 Dibutyl phthalate 1.0

100.0 Example 2 Xylol 25.0 Carbon tetrachloride 5.0 Hydrogenated naphtha(B. R., 135 to 190 C.) 14.0 Mineral spirits (B. R., to 225 C.) 22.0 Highboiling naphtha (B. R.., to 180 C.) 10.0 Turpentine 15.0 Diethyleneglycol monobutyl ether 9.0

The cleaners may be applied to the old surface by means of a brush,cloth pad, or any other convenient way, and particularly good resultsare obtained if a small area is treated at one time. After the surfacehas been wetted liberally with the cleaner, it is wiped dry with a cleancloth at once until the finish is dry and clean. Usually, oneapplication-is sufiicient, but where the old finish is in very poorcondition or where heavy coats of polishing wax have been used, a secondapplication is sometimes necessary. The work is thenready forrefinishing.

The cleaners are also valuable for preparing surfaces in which the oldfinish has disappeared entirely in places. In such cases, the cleanermay be used with sand paper in order. to remove the rust spots. In caseswhere this is necessary, it is advisable to go over the surface aftersanding with a cloth saturated with the cleaner in order to fiow thesanding scratches together and thereby avoid the subsequent use of asealer.

The above formulas are given to illustrate the invention. However, manyof the ingredients may be varied both with respect to amount and kind.This is particularly true of the volatile tar and grease solvents. It isimportant how'- ever to have a relatively large percentage of suchsolvents present and a much smaller percentage of butyl lactate or itsequivalent and a still smaller percentage of solvent plasticizer in thecomposition. The invention is illustrated by the use of butyl lactate asthe typical second class ingredient since it is relatively easy toobtain and is not as expensive as some of the other solvents which maybe used in this class. These compounds should represent between 5 and ofthe composition. In determining the equivalents which may be substitutedfor butyl lactate.

it has been found that the following test serves for a qualitativeevaluation of the emciency of a given compound as an activator. A filmcomposed of 10 parts of camphor and 90 parts of nitrocellulose having aviscosity characteristic of 16 seconds and a nitrogen content of 12.3%is cast on a glass plate from a solution in volatile solvents to give adry film having a thickness of .003 inch. The film when dry is removedand cut into pieces. These pieces are placed on a felt pad saturatedwith the activator being tested and the finger is rubbed lightly butcontinuously over the surface of the film. In order to prevent loss ofthe liquid during the test, the felt pad is placed in a semi-closedcontainer. The time for penetration of the activator is that at whichthe liquid has softened the dry film sufilciently to give it a softtacky surface which is easily detected by the moving finger.

The following table represents results obtained according to this testusing a number of activators:

Penetration time. seconds Ethylene glycol monomethyl ether 46 Amylacetate Ethylene glycol monoethyl ether 61. Diacetone alcohol Butylpropionate Ethyl lactate 104 Ethylene glycol monobutyl ether 112 Butyllactate 122 Methyl cyclohexanone 152 Ethylene glycol monomethyl etheradipate- 220 Diethylene glycol monoethyl ether 235 Diethylene glycolmonobutyl ether 270 Di-n-butyl adipate 480 Tributyl phosphate 520Dimethyl phthalate 1,080 Diethyl phthalate-no softening of film up to1,800 Dibutyl phthalate-no softening of film up to 1,800

with reference to the above table. an activator possessing a penetrationtime within the range of 104 to 270 seconds may be utilized in thecomposition of this invention.

It is therefore apparent that the cellulose 2,1ee,o24 I nitratesolventjgor- {plurality 51 solvents which may be employed' 'in brder.that 'the composition be effective as described shouldha've a solvencypower not substantl'allyi ln, excess of that e;- hibited by ethylIactateand-atleast as great as that exhibited by diethylene glycolmonobutyl ether.

Another important factor ii -the. "evaporation rate of the activator.The following :test may be used in comparing the volatility..using"amylacetate as an arbitrary standard: '2- cc;"' of the liquid to be testedare placed at roomatemp'erature in a tared, open metal cup 2 inchesglhdiameter and 1 inch deep. These cupsi'a're placed on a turntable whichrevolves at about 1 R. P. M. The apparatus also includes a guard about 3inches high around the perphery'of the turntable, and attached to itonly at a few points to afford support, in order to prevent directdrafts. At regular intervals, weighings are made to determine the lossby evaporation. This loss is calculated on a percentage basis andcompared with the loss of amyl acetate. It has been found convenient toassign the arbitrary figure of to amyl acetate.

The following table gives these values on this basis for some of theactivators which have been tested:

On the basis of the above tests, it has been determined that thecellulose nitrate solvent should not have an evaporation ratesubstantially greater than that exhibited by ethyl lactate in order thatthe cellulose nitrate solvent ingredients of the composition remain onthe film surface for a suflicient period to fulfill its expressedfunction of suitably activating and softening the old surface film tothe extent that sufiicient surface flow takes place to smooth outirregularities which would otherwise give an unsightly finish. Thesolvency characteristic of this ingredient is defined above and providesan interdependent limitation for the specific class of cellulose nitratesolvents which have been found satisfactory in the present composition.

As "blanketing agents other materials possessing properties similar tothe dibutyl phthalate may be substituted in whole or in part therefor.Dimethyl phthalate, diethyl phthalate, tributyl phosphate, dibutyltartrate, dibutyl adipate, the phthalate ester of ethylene glycolmono-methyl ether, etc., are illustrative of the type of materials thatmay be utilized in place of the dibutyl phthalate or as a substitutionin part therefor.

In certain cases where the solvent ingredient of the composition has asufllciently low evaporation rate, approaching that of dibutylphthalate, it is possible to eliminate the separate blanketing agent"ingredient, since under these conditions the solvent constituent may, inaddition to providing the desired activating action on the old film,function as a blanketing agent.

If the so-called blanketing agent is omitted,

the amount of nitrocellulose organic solvent required varies betweenapproximately 5 and 10%. If the amount of this ingredient issubstantially less than 5%, neither the solvent action nor blanketingefiect' is adequate for best results and if the proportion of solvent isincreased substantially above 10%, the old film is softened beyond thedesired point because of the greater solvent action and longer period ofexposure of the film to the cleaner. Ingeneral if no blanketing agent isprovided. it is preferred to use proportions of a less active solventnear the upper limit of the range indicated, since under theseconditions, the cleaner can be kept in contact with the old film for asufiicient length of time to permit a more complete removal of thegrease and tar without causing too great softening of the old film.

The cleaning composition described herein may be utilized for cleaningand preparing old lacquer, baked enamel and synthetic resin finishes forrefinishing, and is particularly adaptable to the treatment of oldcellulose nitrate composition surfaces prior to refinishing. Iteliminates sanding of the old finish, which means a definite saving intime and labor, and also disposes of all possibility of swelling" ofsandpaper scratches. It avoids the appearance of welts and the need fora sealer coat. It insures a clean surface for refinishing and, due toits slight solvent action, it activates the old lacquer and promotesadhesion of the new finish.

It is apparent that many different embodiments of this invention may bemade without departing from the spirit and scope thereof and it is,therefore, not intended to be limited except as indicated in theappended claims.

I claim:

1. A cleaning composition for preparing coated surfaces for refinishing,comprising hydrocarbon diluents having a boiling range of about 135 C.to 225 C. in major proportion, about 5 to 10% by weight of an organicsolvent for nitrocellulose having a solvent power at least equal todiethylene glycol monobutyl ether and less than ethyl lactate, saidorganic solvent having an evaporation rate not greater than that ofethyl lactate,

and about 1% of a substantially non-volatile liquid nitrocelluloseplasticizer.

. 2. Composition of claim 1 in which the organic solvent is butyllactate.

3. Composition of claim 1 in which the nitrocellulose plasticizer isdibutyl phthalatep 4. A cleaning composition for preparing coated oldsurfaces for refinishing comprising hydrocarbon diluents having aboiling range of about 135-225 C. in major proportion, and about 5 to10% by weight of organic solvents for nitrocellulose having a solventpower at least equal to diethylene glycol monobutyl ether and less thanethyl lactate, said organic solvent having an evaporation rate notgreater than that of ethyl lactate.

5. A cleaning composition for preparing coated surfaces for refinishingcomprising about to 75 parts by weight of hydrocarbon diluents having aboiling range of about -225 C., 15 parts by weight of turpentine, and 5to 10 parts by weight of an organic solvent fornitrocellulose having atleast as great a solvent power as diethylene glycol monobutyl ether butnot substantially greater than ethyl lactate, said solvent having anevaporation rate not greater than that of ethyl lactate.

6. A cleaning composition for preparing coated surfaces for refinishingcomprising '76 parts by weight of hydrocarbon diluents having a boilingrange of about 135-225 0., 15 parts by weight of turpentine and 9 partsby weight of diethylene glycol monobutyl ether.

7. A cleaning composition adapted for preparing old coated surfaces forrefinishing having approximately the following formula:

Percent by weight Xylene 30.0 High boiling naphtha (boiling range toMineral spirits (boiling range 150 to 225 C.) 21.0 Hydrogenated naphtha(boiling range 135 to C.) 17.0 Turpentine 15.0 Butyl lactate 6.0 Dibutylphthalate 1.0

GEORGE R. ENSMINGER.

